Headers are devices that are mounted to and across the front of agricultural combines to cut crop plants and direct them toward a crop-receiving opening of the combine for threshing, separating and cleaning inside the combine.
Some headers use a reciprocating cutter bar or knife that is disposed across the leading edge of the header adjacent to the ground. The cutter bar severs the plant stalks close to the ground. A reel is also provided on these headers to control the tops of the plants. The reel pushes the top of the plant rearward, causing the plant to fall into a conveyor. The conveyor directs the plant laterally toward a central portion of the header where there is a crop-receiving aperture. Once the crop passes through this aperture it is received in a crop-receiving aperture of the combine, which further conveys the plant back rearward into the combine for further processing.
There are two common styles of headers. The first of these is called an “auger platform” or “auger header” because it has a long right circular cylindrical steel auger or screw that extends laterally across the width of the header. The auger is mounted for rotation at the rear of the header. This style of header provides a broad, generally flat metal floor or apron along the leading edge of the header that extends fore and aft between the cutter bar and the auger and extends laterally the entire width of the header.
The second of these is called a “draper platform” or “draper header”. A draper header has no stationary apron or floor behind the cutter bar, nor does it have an auger located at the rear of the header. The floor is instead replaced with two generally flat endless loop conveyor belts to move the crop laterally to the middle of the header. The conveyor belts are located immediately behind the cutter bar and extending rearward to the back wall of the header, taking the place of the floor and the auger of the auger header. A central conveyor is located between these two conveyors to receive the cut crop material and covey it rearward into the crop-receiving aperture.
One problem for these headers is gathering the entire crop plant being harvested. Headers are constructed to harvest a wide array of plants, from small shrub-like soybeans plants that are less than 800 mm tall to thick shrub-like European canola plants that can approach 3 m in height. It is difficult to design a header that is capable of harvesting the full range of plant heights. A small header is economical to operate, but may not be able to harvest the largest of crop plants.
For this reason, auger-type headers have been configured to have an extendible cutter bar that can move forward and backward in the direction of travel. When the cutter bar is extended (i.e. when it is moved forward in the direction of travel with respect to the rest of the auger header), it is particularly suited to harvest harvesting tall bushy canola plants. When it is retracted it is particularly suited to harvest short, shrub-like plants or grasses.
To prevent crop material from falling into a gap between the cutter bar and the leading edge of the auger header, a metal sheet is attached to the cutter bar that extends rearward from the back edge of the cutter bar and covers substantially the entire width of the apron when the cutter bar is retracted. When the cutter bar moves to its extended position, however, the metal sheet moves forward with the cutter bar and uncovers the apron while still covering the gap between the apron and the cutter bar. In short, the metal sheet has a constant width, and moves front to back with the cutter bar itself, thereby covering and uncovering the sheet metal apron in front of the auger.
EP 0 726 025 A1 illustrates an example of this design, showing an auger header with an extendible cutter bar having a flat panel fixed to it that slides backward and forward on top of the flat metal floor of the header when the cutter bar extends and retracts. By automatically overlapping the floor of the header with the panel extending from the cutter bar, the cutter bar can be extended and retracted with little extra work.
The Claas Vario header has an extendible cutter bar using a different arrangement. In the Claas Vario header, the cutter bar is extended to create a gap between the cutter bar and the floor of the header. Once this gap is created by extending the cutter bar, the operator then manually inserts an elongate gap-filling metal panel (or panels) that fills the gap. When the cutter bar is retracted, the operator first unbolts the metal panel and removed it to create a gap, and the cutter bar is then retracted. This process requires several additional steps to complete.
Draper headers, however, cannot employ retractable cutter bars due to the location and orientation of their conveyor belts. In a draper header the conveyor belts are located immediately behind the cutter bar in order to permit the draper header to harvest small crops. There is no extended sheet floor of the header that extends between the cutter bar and the conveyor as there is in an auger header, and therefore there is no apron to be covered and uncovered as the cutter bar extends and retracts as there is in an auger header.
Any metal sheet that would cover the gap between the cutter bar and the front edge of the conveyor belt when the cutter bar is extended (such as the metal sheet in the auger header arrangement) would be pulled so far rearward when the cutter bar is retracted that it would partially or completely cover the conveyor belt of the draper header.
On the other hand, if no metal sheet is provided to cover the space between an extended cutter bar and the leading edge of the conveyor belts, then crop will fall into the gap between the cutter bar and the conveyor belts and so drop onto the ground.
For this reason, it has not been possible to provide a draper header with a retractable cutter bar.
The invention disclosed herein solves the technical problem of providing a draper header with an extendible cutter bar, the solution of which is provided by claim 1 by a first configuration and claim 11 by a second configuration. Other beneficial features are claimed in the claims depending therefrom.